The following relates generally to wireless communication and more specifically to latency reduction in unlicensed spectrum.
Wireless communications systems are widely deployed to provide various types of communication content such as voice, video, packet data, messaging, broadcast, and so on. These systems may be capable of supporting communication with multiple users by sharing the available system resources (e.g., time, frequency, and power). Examples of such multiple-access systems include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, and orthogonal frequency division multiple access (OFDMA) systems, (e.g., a Long Term Evolution (LTE) system, or a New Radio (NR) system). A wireless multiple-access communications system may include a number of base stations or access network nodes, each simultaneously supporting communication for multiple communication devices, which may be otherwise known as user equipment (UE).
Wireless multiple-access technologies have been adopted in various telecommunication standards to provide a common protocol that enables different wireless devices to communicate on a municipal, national, regional, and even global level. An example telecommunication standard is LTE. LTE is designed to improve spectral efficiency, lower costs, improve services, make use of new spectrum, and better integrate with other open standards. LTE may use OFDMA on the downlink (DL), single-carrier frequency division multiple access (SC-FDMA) on the uplink (UL), and multiple-input multiple-output (MIMO) antenna technology
A UE and base station may be configured for wireless communication in a shared or unlicensed radio frequency spectrum. The base station may contend for access to the medium during a limited transmission opportunity (TxOp) that may include both DL and UL transmission time intervals (TTIs). In some cases, a base station may send a grant for a UE to transmit UL information, but the UE may not be able to send the corresponding UL transmission during the same TxOp if the grant is not received sufficiently early. The UE may then wait until the next TxOp to send the UL transmission. This may cause disruptions and delays in the communication between the UE and the base station.